1. Field of the Invention
The present invention relates to eductor apparatus. More particularly, the present invention the relates to eductor apparatus whereby a first fluid is mixed with a secondary solid or liquid through the use of a venturi. More particularly, the present invention relates to eductor apparatus whereby lobes are formed on a throat of a diffuser so as to minimize boundary layer formation in the diffuser.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Eductors and jet pumps are designed so as to utilize the Bernoulli principle of when pressure is high, velocity is low and inversely when velocity is high, pressure is low. The term “eductor” or jet pump describes a pump with no moving parts that converts pump pressure into a high-velocity stream (kinetic energy) in order to generate a low pressure. The resulting high-velocity stream produces a low pressure region that draws in and entrains a secondary powder or liquid through the suction inlet (induction port). At the intersection of the issuing motive liquid stream emanating from the nozzle orifice and the secondary additive entering the mixing chamber from the suction inlet, an exchange of momentum produces a mixed stream traveling at a velocity intermediate to the motive fluid and suction velocity. The downstream diffuser section then converts the velocity-pressure back into static pressure at the discharge of the eductor. In addition to mixing a secondary powder or liquid with a motive liquid, these devices are used to convey, compress and mix gases and vapors.
Many eductor and jet pump designs incorporate tabs, skewed swirls and other downstream attachments in the diffuser section to attempt to generate more intense turbulence, thereby attempting to aid to enhance mixing a primary motive fluid with a secondary additive. These obstructions disturb the streamline flow pattern, causing “eddies” and waves that require considerable energy to support them. This energy is drawn from the primary flow-field (bulk fluid stream), thus reducing the energy level in the flow-field and ultimately reducing the diffuser efficiency. These structure formations may cause the boundary layer to prematurely detach from the pipe wall surface. Relatively larger particles will not follow the bulk liquid flow and will collide and collect on any obstacle in the downstream flow-field.
Generally, eductors and jet pumps are described with three components: (1) a nozzle; (2) an induction port (suction); and (3) a diffuser assembled in a housing. However, two of the most important and functional components of an eductor and jet pump are sometimes overlooked. In particular, these are the mixing chamber and the Venturi throat section. The mixing chamber is located between the nozzle orifice discharge and the converging inlet into the Venturi throat. This is the intersecting, comingling and interacting region between the motive fluid and the secondary additive that has been introduced through the induction port (suction). The first stage of mixing occurs in the mixing chamber and the final stage of mixing occurs in the Venturi throat before entering the downstream diffuser section.
The motive nozzle should be designed to produce the highest possible velocity relative to the input energy. The downstream cross-sectional Venturi throat should be designed to provide the strongest suction possible before the fluid enters the diffusion section. The diffuser should be designed to provide the greatest amount of energy recovery during conversion.
The diffuser section of the eductor or jet pump is a diverging duct that is shaped to gradually recover fluid static pressure from a fluid stream while reducing the downstream flow velocity. It is a means of converting kinetic energy into static pressure. During velocity deceleration and the increase in static pressure, it must be noted that if the diffuser angle of discharge is greater than ten degrees, fluid separation from the conduit wall may occur. In many technical articles, the diffuser discharge angle is recommended between seven and twelve degrees. Any higher angle than twelve degrees may cause separation. The diffuser is a pressure recovery tube that is shaped to gradually reduce the velocity and convert the energy into static pressure at the discharge with as little pressure loss as possible.
A key to an efficient and effective diffuser is one that lies in the ability to control the downstream boundary layer and delay detachment. When a flowing fluid stream comes in contact with a stationary surface, a portion of the free-flowing stream velocity is reduced. The free-flowing stream velocity reduction is caused by shear stress between the stationary conduit wall and the moving fluid stream. This frictional flow resistance is known as frictional or viscous drag. A thin layer of fluid adjacent to the conduit or pipe wall surface increases from zero to a mean velocity of the free-flowing stream. The viscous layer near the conduit wall is called the boundary layer. The boundary layer fluid gradually blends into the free-flowing stream.
Diffuser “stall” is the detachment or separation of flow from the diffuser internal surface walls during fluid deceleration causing the formation of “eddies” and a region of unsteady flow within the diffuser. The profile of flow exiting from the diffuser and the diffuser pressure recovery are intimately related to the possibility of diffuser stall. Downstream tendency to wall detachment that leads to diffuser stall can block the diffusion flow causing an unsteady and unstable exit flow that may result in a significant loss of pressure and, if the loss is great enough, a reversal of flow can occur.
Diffuser performance is largely governed by the growth of the boundary layer and the degree to which the flow conforms to the diffuser internal surface walls. An efficient diffuser is one which converts the highest possible percentage of kinetic energy into pressure within a given restriction in diffuser length and expansion ratio (i.e. aspect ratio). The intensity of the flow-field velocity is determined by the motive feed pressure (Reynolds number), the total mass content of the admixture, the mixture density and downstream viscous drag.
FIG. 1 is an illustration of prior art eductor assembly. As can be seen, the eductor assembly 10 in FIG. 1 has an inlet nozzle section 12, a mixing chamber 14 and a diffuser section 16. The inlet nozzle section 12 has a tubular portion 18 that extends to a nozzle 20. The tubular portion 18 defines a primary inlet 22. The primary inlet 22 carries a fluid to the nozzle 20. The nozzle 20 has a wide diameter portion 24 opening to the primary inlet 22 and a narrow diameter opening 26 opening to the mixing chamber 14. The narrow diameter opening 26 is adjacent an end of the nozzle 20 opposite the wide diameter opening 24.
In FIG. 1, it can be seen that the mixing chamber 14 is connected to the inlet nozzle section 12 and is in fluid communication with the narrow diameter opening 26 of the nozzle 20. The mixing chamber 14 has an induction port 28 opening thereto and extending therefrom. In particular, it can be seen that the nozzle 20 has an outer surface 30 that extends greatly into the interior of the mixing chamber 14 and generally flows inwardly of the wall 32 of the induction port 28. As such, the outer surface 30 of the nozzle 20 provides a surface whereby any solids that are introduced into the induction port 28 can accumulate thereon.
The diffuser section 16 has a secondary inlet 24 with a wide diameter end 36 adjacent the mixing chamber 14 and a narrow diameter end 38 formed inwardly thereof. The secondary inlet 34 is the Venturi of the eductor apparatus. A diffuser 40 is connected by a throat 42 to the secondary inlet 34. The throat 42 is of a generally constant diameter. The diffuser 40 has a narrow diameter end 44 at the throat 42 and a wide diameter end 46 at the end 48 of the diffuser 16.
In the past, various patents have issued relating to such eductor apparatus. In particular, U.S. Pat. No. 5,664,733, issued on Sep. 9, 1997 to the present inventor, describes a fluid mixing nozzle and method. In this patent, a first fluid flows therefrom to mix with a second fluid external to the nozzle so as to induce vortex creation and chaotic turbulent flow. The nozzle has a body with a cavity extending therethrough from the inlet end to the outlet end. The cross-sectional area of the inlet orifice of the nozzle is greater than its outlet orifice cross-sectional area. The outlet orifice cross-section area shape has a substantially circular central portion and at least one protrusion extending from the perimeter of the central portion. The protrusions are smaller in cross-sectional area than the central portion and are equally spaced about the central portion perimeter.
U.S. Pat. No. 5,775,446, issued on Jul. 7, 1998 to the present inventor, teaches a nozzle insert for rotary rock bit that has an orifice with a generally circular central region and a plurality of angularly-spaced, non-circular outer regions around the periphery thereof so that flow of mud through each outer region develops a vortex pattern that increases entrainment of rock particles so as to prevent bit balling. It also serves to decreases overbalance pressure to enhance rate of penetration.
U.S. Pat. No. 6,609,638, issued on Aug. 26, 2003 to the present inventor describes a flow promoter that is used to promote flow of material in a hopper or bin container. The flow promoter comprises a body having an inlet orifice, an outlet orifice, and an arrangement of peaks, ridges, slopes and radial lobes provided at the inlet end to cooperatively create stress points in the material. This invention can also include a removable flow promoter that can be inserted into a container.
U.S. Pat. No. 6,796,704, issued on Sep. 28, 2004 to the present inventor, describes an apparatus and method for mixing components with a venturi. This eductor mixing device has a main body or housing of a generally cylindrical shape. An inner tube for one component to be mixed with a liquid is mounted in the main body with a vortex chamber formed in an annulus between the main body and the inlet flow tube. Pressurized liquid enters the vortex chamber through a generally rectangular entrance opening along an arcuate surface which smoothly merges with the cylindrical surface of the main body. A liquid in a swirling motion moves in a descending helical path about the inner tube and passes through a gap between coaxial frusto-conical surfaces of the converging inner nozzle of the inner tube and an outer coaxial liquid nozzle of the diffuser ring. A high velocity is created by the swirling liquid for exerting a suction or negative pressure at the lower end of the inner nozzle so as to draw the component to be mixed into the swirling liquid stream where the swirling liquid and particulate material form a strong vortex to create a slurry in a minimal travel distance after passing the inner converging nozzle of particulate inner tube.
U.S. Pat. No. 6,024,874, issued on Feb. 15, 2000 to the present inventor, shows a hydrocyclone separator. This hydrocyclone separator has an outer housing having an upper housing portion and a lower housing portion. The upper housing portion has a cylindrical chamber and an involuted entrance to the cylindrical chamber. The vortex finder tube has a flaring lower end portion. A solid core is mounted within the finder tube and extends downwardly from the finder tube a distance equal to one and a half times the inner diameter of the entrance orifice of the finder tube.
U.S. Pat. No. 6,000,839, issued on Dec. 14, 1999 to the present inventor, provides a continuous static mixing apparatus that includes mixing disks. Each of the mixing disks has a set of symmetrically distributed nozzles therein that accelerate the flow and that create mixing turbulence in the flow. Typically, the mixing apparatus combines the outlet flows of the mixing disks to provide a collision therebetween and, thus, increase turbulence and mixing. Communication passageways connect the material supplies to the mixing apparatus and direct the materials through the mixing disks.
U.S. Pat. No. 5,322,222 issued on Jun. 21, 1994 to the present inventor, teaches a spiral jet fluid mixer for mixing fluids. This spiral jet mixer has an elongated body with a first inlet nozzle for introduction of a primary fluid. A mixing chamber is provided having a diverging wall and a converging wall. A plurality of angled, helical passageways in the diverging wall allows the introduction of a secondary fluid into the mixing chamber in a spiraling turbulent, initially convergent flow pattern.
U.S. Pat. No. 4,971,768 issued on Nov. 20, 1990 to Ealba et al., shows a diffuser with convoluted vortex generator. A thin, convoluted wall member disposed upstream of the inlet of a diffuser so as to generate large-scale vortices having axes in the downstream direction. The vortices enhance mixing within the diffuser and can also energize the boundary layer. This improves diffuser performance and delays the onset of stall.
U.S. Pat. No. 7,251,927 issued on Aug. 7, 2007 to J. H. Anderson, discloses a second stage external jet nozzle mixer that has identically formed lobes which equal in number the lobes of the first stage internal mixer. The external mixer works with the internal mixer and furthers the mixing of the jet engine internal bypass flow with the internal jet engine core flow. This mixing levels the disparate flow velocities attendant with the jet engine exhaust, reduces the peak velocities from the jet engine core and increases the lower bypass velocities of the jet engine internal bypass flow. The lobes include complex curvatures that greatly enhance mixing of the gases and ambient cooling air so as to reduce noise.
It is an object of the present invention to provide an eductor apparatus that provides the ability to control downstream boundary layers and to delay detachment.
It is another object of the present invention to provide an eductor apparatus that enhances the ability to convert the highest possible percentage of kinetic energy into pressure within a given restriction in diffuser lengths and aspect ratio.
It is still a further object of the present invention to provide an eductor apparatus with improved radial velocity in the throat.
It is a further object of the present invention to provide an eductor apparatus that serves to keep the boundary layer thin with respect to the bulk flow field.
It is another object of the present invention to provide an eductor apparatus that minimizes pressure losses in the diffuser.
It is still a further object of the present invention to provide an eductor apparatus that enhances the mixing process.
It is a further object of the present invention to provide an eductor apparatus that produces dynamic stretching and folding so as to cause intense mixing interactions.
It is a further object of the present invention to provide an eductor apparatus that energizes the boundary layer so as to reduce frictional drag so as to cause improved suction.
It is still a further object of the present invention to provide an eductor apparatus with a recessed nozzle that does not obstruct the mixing chamber or allow solids to be accumulated on the exterior surface of the nozzle.
It is still a further object of the present invention to provide an eductor apparatus that allows larger material to be inducted into the mixing process.
It is still a further object of the present invention to provide an eductor apparatus that avoids plugging.
It is still a further object of the present invention to provide an eductor apparatus that effectively mixes and emulsifies.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.